Weighing apparatus

ABSTRACT

Weighing apparatus incorporated in a vehicle to be responsive to the load on the vehicle axle(s) and to be used when the vehicle is in motion. Mechanical low-pass filtering means are provided to attenuate sudden variations of the relative displacement between the vehicle&#39;&#39;s load carrying structure and axle(s) at least when the moving vehicle is heavily loaded so that only the average value of this varying relative displacement is utilized in giving an indication of the load carried by said structure.

United States Patent Bishop Mar. 14, 1972 [54] WEIGHING APPARATUS3,142,349 7/1964 Blodgett ..177/210 X 3,151,692 10/1964 Dysart ..177/138[72] inventor. Brian L. H. Bishop, WItney, England 3,167,142 H1965Meneely W177 37 [73] Assignee: Smiths Industries Limited, London, En-3,314,491 4/1967 Nelson ..l77/138 gland Primary Examiner-Richard B.Wilkinson [22] 1970 Assistant Examiner-George H. Miller, Jr. [21] Appl.No.: 54,939 Attorney-William D. Hall, Elliott I. Pollock, Fred C.Philpitt, George Vande Sande, Charles F. Steininger and Robert R. [30Foreign Application Priority Data pr'ddy July 18, 1969 Great Britain;..36,2l2/69 S C Weighing apparatus incorporated in a vehicle to beresponsive ..l77/l37,l77/lzt6ll7Z/92"1)g to the load on the vehicleaxle(s) and be used when the [58] d I84 vehicle is in motion. Mechanicallow-pass filtering means are 0 re 2 provided to attenuate suddenvariations of the relative displacement between the vehicles loadcarrying stmcture and axle(s) at least when the moving vehicle isheavily loaded so (56] References cued that only the average value ofthis varying relative displace- UNlTED STATES PATENTS ment is utilizedin giving an indication of the load carried by said structure. 3,092,8186/1963 Potschka ..177/l 37 X 3,109,505 11/1963 Davis et al. ..177/137 18Claims, 6 Drawing Figures PAIENTEDMAR14 1912 3,648,790

SHEEI 2 OF 4 arh m "7. B5

jlmlerr/ WEIGHING APPARATUS This invention relates to weighing apparatusand in particular to weighing apparatus of the kind adapted or intendedto be incorporated in a vehicle so as to be responsive to variations inthe load carried by the vehicle.

One type of apparatus of this kind, comprises an electrical indicator(preferably having a pointer cooperating with a scale) and a sensorcomprising two relatively movable elements (for example a contactelement arranged for wiping engagement of an electrical resistanceelement to vary the effectiveelectrical resistance of the latter) whoserelative movement (hereinafter referred to as the induced relativemovement) produces a varying electric signal and is directly related tothe relative movement between the load-carrying structure of the vehicleand the road. Generally speaking the relative movement between theload-carrying structure and the road is equivalent to changes in theposition of the load-carrying structure relative to the road wheelsand/or to the axles of the .vehicle, the axles supporting theload-carrying structure through springs whose vertical deflections arerelated to the total vertical forces acting on the springs.

Prior proposals for this type of apparatus have apparently assumed thatthe vertical deflections of the springs are at all times directlyrelated to the total load, i.e., to the weight of the load-carryingstructure plus the load (if any) carried thereby. The applicants hereinhave now realized that, at least as concerns certain forms of spring, inparticular leaf-springs, this fundamental assumption does not take intoconsideration the temporary indeterminancy of the settling-position ofthe springs when the vehicle is stationary, which indeterminancy isbelieved attributable to the indeterminate variations in striction orfriction, in particular between the leaves of leaf springs, and thattherefore the indications of load given by the indicators of these priorproposals would be indeterminate and usually inaccurate when obtainedwith the vehicle stationary.

lt will be readily apparent that a single indicator can be used for aplurality of sensors that are each responsive to a proportion of thetotal vertical forces (hereinafter referred to as the proportionalforces) acting on the springs, the average value of these proportionalforces, which are not constant when the vehicle is in motion, beingdirectly related to the proportion of the total load (hereinafterreferred to as the proportional load) producing them. Therefore as usedhereinafter, the termprimary relative movement is intended to mean theeffective proportion of the relative movement between the load-carryingstructure and the road that produces the induced relative movementbetween the two elements of a particular sensor.

According to one aspect of this invention there is provided a sensor forapparatus of the said one type that is intended to be utilized when thevehicle is in motion, which sensor has associated therewith mechanicallow-pass filtering means to attenuate sudden variations of the primaryrelative movement 'which would otherwise produce sudden variations ofthe induced relative movement. In use, sudden variations of the primaryrelative movement could be caused by vehicle motion over a non-smoothterrain, for example a rough or pot-holed road.

Preferably the mechanical low-pass filtering means comprises springmeans to transmit the primary relative movement or a fixed proportionthereof to an intermediate member at least when the proportional forcesexceed a predetermined value; and mechanical damping means, actuable bymovement of said intermediate member or a part rigidly connected theretoand comprising two relatively movable components to be disposed suchthat, in use, the induced relative movement is substantiallyproportional to the relative movement between said'two components.

Preferably one of said components is rigidly connected to one of saidelements for movement therewith; and the other of said components isrigidly connected to the other of said elements.

The mechanical damping means may comprise a variable volume chamber. Inone arrangement the variable volume chamber is a flexible bellows havingrigid end closure walls one of which is provided with a bleed aperture.One or other of said end closure walls may constitute said intermediatemember or a part rigidly connected thereto. Preferably at least part ofone of said elements is disposed within said flexible bellows;preferably both said elements are wholly disposed within said flexiblebellows. In another arrangement the variable volume chamber comprises acylinder closed at one end by a flexible diaphragm and containing afluid acted upon by a member constituting one of said components.

Preferably said spring means reacts against and/or between saidintermediate member or a part movable therewith and an abutment memberintended in use to be abutted by a part of or rigidly connected to thevehicle axle or the load-carrying structure only when the proportionalforces exceed said predetermined value. Restraining means may beprovided to restrain said abutment member from abutting the part of orrigidly connected to the vehicle axle or the load-carrying structurewhen the proportional forces are below said predetermined value.

By arranging the spring means to transmit the primary relative movementonly when the proportional forces exceed a predetermined value, thesensor is only continuously operative when the proportional load isabove a predetermined value (corresponding to a predetermined value ofthe average of the proportional forces), and therefore, if the twoelements of the sensor are always in engagement with one another, therisk of excessive wear of the elements is reduced. Furthermore, if thepredetermined values of the proportional load and of the average of theproportional forces are each near the upper desired limit which thatproportion may safely reach, the electrical indicator of the apparatusof which the sensor forms a part may be calibrated so that the pointermoves over substantially the whole scale as the proportional load variesbetween its predetermined value and its upper limit.

One form of two-element sensor is of an inductive character comprising arotary or a linear differential transformer. The transformer maycomprise an E-transformer having two oppositely would coils each on anextreme limb of the E (constituting one element) and a magnetizable bar(constituting the other element) disposed between the magnetic poles atthe limb ends for movement relative to the limbs. Alternatively thetransfonner may comprise a ferrite rod relatively axially movable withina cylindrical coil former that has a central primary winding thereuponto be fed with a constant amplitude alternating voltage and has twosymmetrically wound secondary windings thereupon disposed one each sideof the primary winding and electrically connected in opposition.

However a preferred form of two-element sensor is of the rheostat typein which a contact element is arranged for relative wiping engagement ofan electrical resistance element. Preferably the electrical resistanceelement is coiled about a generally cylindrical former. In a convenientarrangement in which the induced relative movement is angular, theformer is provided externally with a rib or bead that follows a helicalpath about the longitudinal axis of said former and has a small helixangle, preferably of the order of 20, so that small changes in saidformers angular position can result in comparatively substantial changesin the effective resistance of the electrical resistance element.

According to another aspect of this invention there is providedapparatus of the said one type that is intended to be utilized when thevehicle is in motion, comprising a sensor according to said one aspectof the invention and an electrical indicator, which preferably comprisesa moving-coil type of movement.

By way of example, embodiments of this invention will now be describedwith reference to the accompanying drawings of which:

FIG. 1 shows schematically a first embodiment mounted beneath aload-carrying structure of a vehicle when viewed along the vehicleslongitudinal axis.

FIG. 2 is a cross-sectional view taken along the line II-Il of FIG. 1;

FIG. 3 is a similar view to that of FIG. 1 of a second embodiment;

FIG. 4 is a longitudinal cross-sectional view of a third embodiment;

FIG. 5 is a cross-sectional view taken along the line V-V of FIG. 4; and

FIG. 6 is a schematic perspective view of part of said third embodiment.

Referring firstly to FIGS. 1 and 2, the vehicles load-carrying structure10 is supported at the rear of the vehicle on thevehicles rear axle(s)through leaf springs disposed longitudinally of the vehicle at the endsof the or each rear axle. The load-carrying structure 10 has securedthereto (via a ball-andsocket connection 11) the upper end of the outertubular casing 12 of a rheostat unit 13 that comprises a coiledresistance element and a contact element for wiping engagement of thecoiled resistance element. One of the elements is fast with orconstituted by a spindle 14 movable longitudinally within the casing 12to thereby vary the effective electrical resistance of the rheostat unitwhen connected in an electrical circuit by the leads 15. The lower endof tubular casing 12 is secured to the rigid, double-skinned upper endclosure wall 16 of a flexible bellows 17 whose rigid, double-skinned,lower end closure wall 18 is secured to the spindle 14 (which latter isthereby partially enclosed by the bellows 17). An air bleed aperture 19is provided in wall 16 and if desired a variable constricting device 20may be provided for the air bleed aperture 19. The upper and lower endclosure walls 16 and 18 of the bellows 17 form its two relativelymovable components, the former being vertically immovable with respectto the load-carrying structure 10.

The lower end closure wall 18 is secured to one end of a ball-and-socketconnection 21 whose other end is secured to one limb of an L-shapedbracket 22. The other limb of bracket 22 is clamped to the centralportion 23 of a generally U- shaped high rate spring 24 whose legs areoppositely coiled and clamped at their ends 33 to a beam 25. The beam 25comprises an elongated U-shaped frame whose legs 26 are secured at oneend to a pin 27 that is pivotally mounted in a bracket 28 rigidlysecured to the load-carrying structure 10. A spring 29 coiled about thepivot pin 27 serves to urge the beam 25 downwardly. Adjacent the otherend of the legs 26 there is provided a small wheel 30 pivotally mountedbetween the legs on a pivot pin 31 and disposed directly above a centralportion of one rear axle of the vehicle (not shown) yet verticallyspaced therefrom. A chain 32 (omitted from FIG. 2) whose ends aresecured to the load-carrying structure 10 and the non-pivotted end ofbeam 25 serves to restrain the beam 25 from pivotting about pivot pin 27to a position further clockwise than that shown in broken lines.Alternatively a flexible cable wire may replace chain 32.

In use, when the proportion of the total load affecting said one rearaxle is increased, the proportional forces thereby induced cause therear leaf-springs to be depressed so that the load-carrying structuremoves nearer said one rear axle and the road. Transmission of thisprimary relative movement to the rheostat unit 13 is only commenced whenthe vertical separation between the rear axles central portion and thewheel 30 is taken up. Thus an indication of the proportional load willonly be obtained from the electrical indicator (connected via thecircuit to lead 15) when the load is above some predetermined value,preferably near the maximum desired safety limit for this load. It willbe appreciated that readings are taken of the electrical indicator whilethe vehicle is in motion so that, as explained above, the transmittedprimary relative movement (equivalent to the vertical depression of theleaf-springs), that produces the induced relative movement between thetwo elements of the rheostat unit (which induced relative movement givesrise to indicator pointer deflection), is related to the proportionalload. However, although the proportional forces are continuously varyingbecause the vehicle is in motion over bumps and pot-holes in the road,the average value of these varying proportional forces is substantiallyequivalent to the proportional load and it is this average value thatcauses the two elements of the rheostat unit 13 to take up relativepositions which are substantially non-varying for a constantproportional load greater than the predetermined value of proportionalload. In operation, once the vertical separation between the axle scentral portion and the wheel 30 is taken up, the primary relativemovement is equivalent to the vertical displacement of the wheel 30(which can move generally vertically because the pivotted beam 25 islonger than this primary relative movement) and is thus proportional tothe vertical displacement of the clamped leg ends of spring 24. In thesteady state i.e., the theoretical state when the proportional forcestransmitted are constant at their average value), the verticaldisplacement of the clamped leg ends of spring 24 is equivalent to thevertical displacement of the central portion 23 of spring 24 and istransmitted to the bellows lower end closure wall 18 which latterthereby serves as the aforesaid intermediate member. The verticaldisplacement of wall 18 (which in the non-steady state is varying) ismechanically damped by the flexible bellows l7 and this damped verticaldisplacement is transmitted to the spindle 14 which causes the rheostatelement secured to it to move with respect to the other rheostat elementsecured to the rheostat outer casing 12. Thus an induced relativemovement between the two rheostat elements is produced that is equal tothe relative movement between the two end closure walls of the bellows(acting as the aforesaid mechanical damping means) and is directlyproportional to the primary relative movement.

It will be appreciated that the ball-andsocket connections 11 and 21 areprovided to allow for lateral misalignments. If desired the abovedescribed embodiment may be modified by inversion and mountingpermanently on the central portion of the axle instead of theload-carrying structure so that it will come into operation when thebeam 25 is abutted by the underside of the load-carrying structure or apart secured thereto.

In the second embodiment (shown in FIG. 3) the load-carrying structureis supported at the front of the vehicle's front axle(s) throughleaf-springs disposed longitudinally of the vehicle at the ends of theor each front axle. The front axle comprises an I-section girder 40extending transversely across the vehicle. One end portion 41 of anelongate abutment member 42 is held continuously in contact with thegirder 40 by a high rate coiled tension spring 43 acting between theabutment member 42 and a bracket 44 secured to the girder. The other endportion 45 of abutment member 42 is pivotally mounted at 35 to one end46 of a rodlike beam 48 whose other end 47 is welded as at 49 to acentral component 50 irrotatably fixed to the vehicle 's load-carryingstructure.

A flexible bellows 55 has end closure walls 51 and 52 (serving as theaforesaid components of the mechanical damping means) moulded ofsuitable plastics material rigidly with splined metal spindles 53 and 54respectively that project a short distance outwardly of the bellows 55through the end closure walls. The longer spindle 54 is longitudinallyslidable within the central bore 56 of a hollow cylindrical drum 57moulded integrally with the end closure wall 51. The drum 57 extendsinwardly of the bellows and an electric resistance element 58 is formedby winding a coil about the outer surface of the drum, which wire coilis engaged by a wiper contact element 59 supported by the end closurewall 52. An air bleed aperture 60 is provided through end closure wall51, and a small coiled spring 61 surrounds the spindle 54 and actsbetween end closure wall 52 and the inner end face of drum 57 to urgethe end closure walls 51 and 52 towards their maximum separation. Thusthe two elements 58 and 59 are wholly enclosed within the bellows 55 andform a rheostat unit whose effective resistance depends on the relativeposition of the end closure walls 51, 52 and consequently on therelative positions of the elements 58, 59 respectively secured thereto.

The projecting end of short spindle 53 is pivotally mounted at 62 to thebeam 48, and the projecting end of long spindle 54 jacent its pivot 35.

In use, an increase in the proportional forces induced in the frontleaf-springs cause them to be depressed so that beam 48 moves nearer thefront axle and the road. This primary relative movement causes abutmentmember 42 to pivot about 35 and results in a generally verticaldisplacement of its opposite end portion 41 and a proportionally smallergenerally vertical displacement of the end 64 of blade spring 65. In thesteady state the vertical displacement of the blade spring end 64 isequivalent to the vertical displacement of the other end 63 of bladespring 65 and this displacement, through the agency of spindle 54 whichserves as the aforesaid intermediate member, causes end closure wall 52together with wiper contact 59 to alter their positions relative to endclosure wall 51 and to resistance element 58. The displacement of wall52 (which in the non-steady state is varying) is mechanically damped bythe flexible bellows 55. Thus an induced relative movement between thetwo elements 58 and 59 is produced that is equal to the relativemovement between the two end closure walls of the flexible bellows 55and is directly proportional to the primary relative movement itselfdirectly related to the change in proportional forces affecting thefront axle. Thus as long as the indicator is read while the vehicle isin motion, an indication may be had of the proportional load on thefront axle (which proportional load induces the proportional forces) byconnecting the indicator in circuit with the effective resistance of therheostat winding 58.

It will be appreciated that to further minimize wear of the elements 58and 59 a lost-motion device may be provided in the mechanismtransmitting the primary relative movement to the elements. This may besimply done by providing a vertical spacing between the girder 40 andthe end portion 41 of adjustment member 42. Alternatively the coiledwinding 58 may be stopped short a predetermined distance from the endface of drum 57 adjacent end closure wall 52. In either event theelectrical indicator may be suitably calibrated so that its minimumreading corresponds to the predetermined value of the proportional load.

Furthermore, it will be appreciated that two assemblies such as thatshown in FIG. 3 may be provided which are each welded as at 49 to thecasing of a vehicles front-wheel stub axle, in which case readings ofthe suitably calibrated electrical indicator will correspond to theproportional load on each front wheel, suitable switching arrangementsbeing provided between the electrical indicator and the elements 58 and59 of the rheostat unit.

In the embodiment of FIGS. 4 to 6, the unit there shown in a casthousing 70 may be mounted rigidly with the load-carrying structure by aplate 71 cast integrally with the housing. An input shaft 72, supportedfor rotation in bearings 73 in a housing end wall 74, is coupled to apivot pin secured to one end of a beam (such as the pivot pin 27)secured to the beam 25 of the first embodiment) or to one end of anabutment member (such as the pivot 35 secured to the abutment member 42of the second embodiment), the opposite end of the beam or abutmentmember being vertically displaceable in accordance with the primaryrelative movement (at least when the proportional forces causing thisprimary relative movement exceed a predetermined value) to therebyprovide a corresponding small angular displacement of the pivot pin andthe shaft 72.

Within the housing 70 a high rate spiral spring 75 has its inner end 76secured to the inner end of shaft 72 and its outer end 77 secured to ananchor post 78 (FIG. 6) extending longitudinally from the end 79 of aradially projecting arm 80 that is integral with a generally circularplate 82. Plate 82 is secured by screws 81 to a generally cylindricaldrum 84 moulded of a suitable plastics material integrally with aprojecting bead 85 and about a central spindle 86. Spindle 86 isrotatable in a fixed longitudinal position by being journaled at one end83 in a recess in the end of input shaft 72 and at its opposite end 87in a bearing housing 88which is staked centrally to a back plate 90itself secured by long bolts 89 to the housing end wall 74. The head 85follows a helical path about the longitudinal axis of drum 84 (andtherefore of spindle 86 and of input shaft 72) and has a small helixangle (i.e., a large pitch) preferably of the order of 20 of arc. Anelectrically resistive wire (not shown) and constituting one element ofthe rheostat is closely coiled about the surface of drum 84 so as tohave a large number of convolutions each having a small region overlyingthe bead 85 and has one end electrically connected to a conducting pin91 projecting through and insulatingly mounted in the back plate 90. Theother element of the rheostat is constituted by the base of a U-shapedwire frame 92 whose leg ends 93 are coiled about a mounting post 94(having an encompassing sleeve of insulating material) mounted betweenthe housing end wall 74 and the back plate 90. A coiled torsional spring96 surrounds the insulated mounting post 94 and has one end hookedaround the frame leg end 93 adjacent plate 82 and its other end securedto a conducting pin 97 insulatingly projecting through and secured tothe back plate 90. Spring 96 thus serves both to urge base 95 intoconstant abutment with the resistive wire regions overlying bead 85, andalso to electrically connect the base 95 to the conducting pin 97. Itwill be appreciated that the point or small area of contact between theframe base 95 and the resistive wire region overlying bead 85 adopts aposition longitudinally of cylindrical drum 84 that depends on theangular position of cylindrical drum 84. Since the bead 85 has a smallhelix angle, a comparatively small change in the said angular positioncauses a substantial change in the said longitudinal position andconsequently a substantial change in the effective resistance of therheostat.

The angular movement of the cylindrical drum 84 is clamped by mechanicaldamping means 100 (FIG. 5) connected by means of an actuating rod 101 tothe anchor post 78 on the opposite side of arm 80 to spiral spring 75.The end of actuating rod 101 remote from anchor post 78 is sealingsecured to the central region of a flexible diaphragm 102 of rubber orsimilar material, the perimeter of which is supported by the rim 103 ofa cup-shaped support member 104. The outwardly directed flange 106 of acylindrically walled closure 107 of generally U-shaped cross section isswaged over the diaphragm perimeter and the rim 103 to provide avariable volume chamber or enclosure that is filled with a siliconefluid during assembly. Within chamber'105 a disc 108 is so disposed thata small annular gap exists between the rounded edge of the disc 108 andthe cylindrical wall of closure 107, the disc 108 being centrally stakedto a pin 109 screwed into the actuating rod 101 axially thereof. AnO-ring seal 110 and washer 112 surmount the closure flange 106externally thereof and a circlip 113 retains all three in a fixedrelationship with respect to an annular support step 111 formed as aflange in the cast housing 70.

As shown in FIG. 4, the housing 70 is closed by a wall 114 bolted on toa threaded extension 118 of bearing housing 88 and is provided with twoinsulated terminals 115, one of which is electrically connected toconducting pin 91 and the other of which is electrically connected toconducting pin 97. O-ring seals 116 and 117 seal the housing 70 againstingress of moisture and dirt.

In use, the small angular displacement of input shaft 72 that isdirectly related to the primary relative movement is transmitted via thehigh rate spiral spring 75 to the plate 82 and the drum 84 rotatabletherewith. The small movements of the plate 82 (which serves as theaforesaid intermediate member) are damped by the mechanical dampingmeans 100 so that under steady-state conditions the plate 82 and thedrum 84 take up an angular position related to the primary relativemovement. As explained above, small changes in the angular position ofdrum 84 result in large changes in the effective resistance of therheostat so that the electrical'indicator connected in an electricalcircuit with this effective resistance (through terminals may have ahigh scale division to unit of proportional load ratio.

It will be appreciated that since the induced relative movement betweenthe rheostats elements is small, little wear results between theseelements. To further minimize wear between the rheostat elements, thehigh rate spiral spring 75 may be assembled in a stressed condition andrestrained from moving out of this condition by the abutment of the end119 of another radially projecting arm 120 that is integral with plate82 with stop means (not shown) that are cast integrally with housing 70.Thus the plate 82 will only be moved when the primary relative movementexceeds a predetermined value corresponding to a rotation of input shaft72 sufficient to unstress spiral spring 75; In this way the indicatorneed only be calibrated so that its minimum scale marking correspondswith the proportional load inducing the predetermined value of theprimary relative movement.

It will be readily apparent that in each of the abovedescribed exemplaryembodiments of the invention the high rate spring means (24, 65, 75)connected in series with mechanical damping means (17 55, 100)constitute mechanical low-pass filtering means.

Conveniently the electrical indicator minimize with each of the abovedescribed exemplary embodiments of the invention comprises a moving-coiltype of movement, and a pointer cooperating with a scale that iscalibrated either in units of weight or in percentage. Preferably thescale is calibrated to read from about 80% to about ll% of the maximumdesired safety limit for the proportional load, the lower valuecorresponding to the predetermined value of the proportional load.

In each of the above-described embodiments the sensor comprises acontact element arranged for wiping engagement of an electricalresistance element to vary the effective resistance of the latter. Sucha rheostat type of sensor may be replaced by an inductive pickup sensorwhich will similarly produce a varying electric signal in accordancewith the relative movement between two elements of the sensor. Theinductive pickup may comprise a rotary or a linear transformer. A lineartransformer may for example comprise an E-transformer" in which thevoltages in two oppositely wound coils each on an extreme limb of the Eare varied by the movement of a magnetizable bar disposed between themagnetic poles at the limb ends. In a preferred modification of thisexemplary linear transformer, a ferrite rod is disposed as an axiallymovable core within a hollow cylindrical coil former having a centralprimary winding that is fed with a constant amplitude alternatingvoltage and having two symmetrically wound secondary windings one eachside (i.e., axially) of the primary winding that are electricallyconnected in opposition. The ferrite core rod is secured to an actuatingrod of nonmagnetic material that is rigidly coupled to an intermediatemember (such as the wall 18 or the spindle 54 of the respective first orsecond embodiments) whose displacement is equivalent to the inducedrelative movement. When the ferrite core is positioned centrally,signals of equal amplitude are fed into both secondary windings and theresultant output signal is zero. Movement of the ferrite core in eitheraxial direction from the central position results in an output signalproportional to position. A phase reversal occurs in this resultantoutput signal as the ferrite core passes through the central position.Because of this phase reversal the output signal may be demodulated by aphase-sensitive rectifier or alternatively and preferably only theoutput voltage changes that occur in one predetermined phase need berectified. Such a linear variable differential transformer can provide ahigh degree of linearity for resultant output voltage (within areasonable voltage range) corresponding to an input of the inducedrelative movement.

It will be appreciated that when each of the above-describedarrangements according to this invention is in use, the vehiclesuspension oscillates vertically as the vehicle is in motion over anon-smooth terrain, and it is the mean (or average) of theseoscillations which is utilized for giving an indication on theelectrical indicator of the load related to that vehicle suspension.

What is claimed is: l. Weighing apparatus to be incorporated in avehicle that has an axle structure, springs acting on said axlestructure, and a load-carrying structure supported by said springs forrelative movement with respect to ground, and to be utilized when thevehicle is in motion; said weighing apparatus comprising a sensor andmechanical low-pass filtering means to be associated with said axlestructure; wherein said sensor comprises a first element and a secondelement relatively movable with respect to said first element; whereinmeans are provided for mounting said first element to one of saidstructures; wherein said mechanical low-pass filtering means comprisesspring means, a member and mechanical damping means comprising a firstcomponent and second component relatively movable with respect to saidfirst component; and wherein there is provided means connecting saidfirst element and said first component to one another, means connectingsaid second element and said second component to one another and to saidmember, and means connecting said member to said spring means.

2. A vehicle having axles; ground engaging wheels mounted on said axles;springs acting on said axles; a load-carrying structure supported bysaid springs for relative movement with respect to ground, whichrelative movement has contributed to it by each axle an effectiveproportion constituting a primary relative movement; and weighingapparatus to be responsive to variations in load carried by the vehicleand to be utilized when the vehicle is in motion, said weighingapparatus comprising:

A. an electrical indicator B. in association with one of said axles, asensor having two relatively movable elements whose relative movement isin use induced by a said primary relative movement to produce acorrespondingly varying signal; and i C. mechanical low pass filteringmeans in association with said sensor to attenuate sudden variations ofthe primary relative movement which would otherwise produce suddenvariations of the induced relative movement, said mechanical low-passfiltering means comprising 1. an intermediate member; 2. spring means totransmit at least a fixed proportion of the said primary relativemovement to said intermediate member at least when the said primaryrelative movement exceeds a predetermined value, and 3. mechanicaldamping means mounted for actuation by said intermediate member andhaving a. a variable volume chamber comprising a cylinder and a flexiblediaphragm forming one end closure of said cylinder,

b. fluid within said chamber, and

c. two relatively movable components disposed so that said inducedrelative movement is substantially proportional to the relative movementbetween said two components, one of said components being a memberhaving a part thereof disposed within said cylinder for action upon saidfluid and another part thereof extending through said flexible diaphragmand connected to said intermediate member.

3. A vehicle having axles; ground engaging wheels mounted on said axles;springs acting on said axles; a load-carrying structure supported bysaid springs for relative movement with respect to ground, whichrelative movement has contributed to it by each axle an effectiveproportion constituting a primary relative movement; and weighingapparatus to be responsive to variations in load carried by the vehicleand to be utilized when the vehicle is in motion, said weighingapparatus comprising:

A. an electrical indicator,

B. in association with one of said axles, a sensor having two relativelymovable elements whose relative movement is in use induced by a saidprimary relative movement to produce a correspondingly varying signal;and

C. mechanical low-pass filtering means in association with said sensorto attenuate sudden variations of the primary relative movement whichwould otherwise produce sudden variations of the induced relativemovement, said mechanical lowapass filtering means comprising 1. anintermediate member,

2. spring means to transmit at least a fixed proportion of the saidprimary relative movement to said intermediate member at least when thesaid primary relative movement exceeds a predetermined value, and

3. mechanical damping means mounted for actuation by said intermediatemember and having a. a variable volume chamber comprising a flexiblebellows having rigid end closure walls, one of said walls being providedwith a bleed aperture, and

b. two relatively movable components coupled to said end closure wallsand disposed so that said induced relative movement is substantiallyproportional to the relative movement between said two components.

4. Weighing apparatus for incorporation in a vehicle having an axlestructure, ground engaging wheels mounted on said axle structure,springs acting on said axle structure, and a load-carrying structuresupported by said springs for relative movement with respect to groundwhereby while the vehicle is in motion the two said structures attain anaverage relative position in accordance with weight imposed on saidload-carrying structure, said weighing apparatus comprising:

a. a spiral spring;

b. means for coupling a first of said structures to one end of saidspiral spring to cause angular displacement of said one end;

c. electrical transducer means for supplying an electric signal inaccordance with said average relative position of the two saidstructures, and comprising 1. a generally cylindrical former having anaxis and an external rib that follows a helical path of small helixangle about said axis,

2. means mounting said former to the other end of said spiral spring forangular displacement of said former about its axis in response todisplacement of said other end,

3. an electrical resistance element coiled externally around said formerand its rib,

4. an elongate contact element, and

5. means mounting said contact element longitudinally of said former forcontacting portions of said electrical resistance element above saidrib;

. damping means having a viscous substance therein; and

e. means for coupling said damping means between said other end of thespiral spring and the second of said structures to damp out suddenvariations in the position of said other end of the spiral springrelative to the second of said structures.

5. A vehicle having axles; ground engaging wheels mounted on said axles;springs acting on said axles; a load-carrying structure supported bysaid springs for relative movement with respect to ground, whichrelative movement has contributed to it by each axle an effectiveproportion constituting a primary relative movement; and weighingapparatus to be responsive to variations in load carried by the vehicleand to be utilized when the vehicle is in motion, said weighingapparatus comprising:

a. an electrical indicator,

b. in association with one of said axles, a sensor having two relativelymovable elements whose relative movement is in use induced by a saidprimary relative movement to produce a correspondingly varying signal;and

c. mechanical low-pass filtering means in association with said sensorto attenuate sudden variations of the primary relative movement whichwould otherwise produce sudden variations of the induced relativemovement,

said sensor being of rheostat type and comprising a generallycylindrical former mounted for angular motion about its longitudinalaxis and provided externally with a rib that follows a helical path ofsmall helix angle about said lon itudinal axis an electrical resistanceelement coiled about sai former, an

an elongate contact element extending longitudinally of said former forwiping engagement of portions of said electrical resistance elementabove said rib.

6. The combination of claim 5 wherein said small helix angle is of theorder of 20 of are.

7. A vehicle having an axle structure, ground engaging wheels mounted onsaid structure, springs acting on said axle structure, a load-carryingstructure supported by said springs for relative movement with respectto ground, and weighing apparatus to be responsive to variations in loadcarried by the vehicle and to be utilized when the vehicle is in motion,said weighing apparatus comprising spring means, first means operativeto couple one of two ends of the spring means to a first of saidstructures, electrical transducer means for responding to relativemovement between the other of said two ends of the spring means and thesecond of said structures to supply an electric signal to said indicatorin dependence upon the position of said other end of the spring meansrelative to said second structure, damping means, second means operativeto couple the damping means between said other end of the spring meansand the second of said structures to damp out sudden variations in saidrelative position, and electrical indicator means responsive to saidelectric signal'to provide a load indication dependent thereon.

8. The vehicle of claim 7 wherein said spring means is prestressed so asto only transmit a proportion of the relative movement between said twostructures to said other end of the spring means when the distancebetween said structures is below a predetermined value.

9. The vehicle of claim 7, wherein the electrical transducer means is ofan electrically inductive character and comprises a linear differentialtransformer.

10. The vehicle of claim 7, wherein said electrical indicator meanscomprises a moving-coil type instrument.

11. The vehicle of claim 7 wherein said first means comprises anabutment member secured to one of said structures for abutment by theother of said structures, and wherein said spring means acts on saidabutment member.

12. The vehicle of claim 11, comprising restraining means to restrainsaid abutment member from abutment by said structures when the distancebetween said structures exceeds a predetermined value.

13. The vehicle of claim 7, wherein the electrical transducer means isof rheostat type and comprises a generally cylindrical former having anelectrical resistance element coiled thereon and a contact elementdisposed for wiping engagement of said electrical resistance element.

14. The vehicle of claim 13, wherein said generally cylindrical formerhas a longitudinal axis, is mounted for angular motion about said axis,and is provided externally with a rib that follows a helical path ofsmall helix angle about said axis; and wherein said contact element iselongate, extends longitudinally of said former, and contacts portionsof said electrical resistance element above said rib.

15. The vehicle of claim 14 wherein said small helix angle is of theorder of 20 of arc.

16. The vehicle of claim 7, wherein said mechanical damping meanscomprises a variable volume chamber.

17. The vehicle of claim 16 wherein said variable volume chambercomprises a cylinder and a flexible diaphragm forming one end closure ofsaid cylinder, fluid being provided withinsaid cylinder; said dampingmeans further comprising a member disposed within said cylinder foraction upon said fluid, and an external actuator extending through saidflexible diaphragm and connected to said other end of the spring means.

18. The vehicle of claim 16 wherein said variable volume chambercomprises a flexible bellows having rigid end closure walls, one of saidwalls being provided with a bleed aperture.

1. Weighing apparatus to be incorporated in a vehicle that has an axlestructure, springs acting on said axle structure, and a load-carryingstructure supported by said springs for relative movement with respectto ground, and to be utilized when the vehicle is in motion; saidweighing apparatus comprising a sensor and mechanical low-pass filteringmeans to be associated with said axle structure; wherein said sensorcomprises a first element and a second element relatively movable withrespect to said first element; wherein means are provided for mountingsaid first element to one of said structures; wherein said mechanicallow-pass filtering means comprises spring means, a member and mechanicaldamping means comprising a first component and second componentrelatively movable with respect to said first component; and whereinthere is provided means connecting said First element and said firstcomponent to one another, means connecting said second element and saidsecond component to one another and to said member, and means connectingsaid member to said spring means.
 2. A vehicle having axles; groundengaging wheels mounted on said axles; springs acting on said axles; aload-carrying structure supported by said springs for relative movementwith respect to ground, which relative movement has contributed to it byeach axle an effective proportion constituting a primary relativemovement; and weighing apparatus to be responsive to variations in loadcarried by the vehicle and to be utilized when the vehicle is in motion,said weighing apparatus comprising: A. an electrical indicator B. inassociation with one of said axles, a sensor having two relativelymovable elements whose relative movement is in use induced by a saidprimary relative movement to produce a correspondingly varying signal;and C. mechanical low pass filtering means in association with saidsensor to attenuate sudden variations of the primary relative movementwhich would otherwise produce sudden variations of the induced relativemovement, said mechanical low-pass filtering means comprising
 2. springmeans to transmit at least a fixed proportion of the said primaryrelative movement to said intermediate member at least when the saidprimary relative movement exceeds a predetermined value, and
 2. springmeans to transmit at least a fixed proportion of the said primaryrelative movement to said intermediate member at least when the saidprimary relative movement exceeds a predetermined value, and
 2. meansmounting said former to the other end of said spiral spring for angulardisplacement of said former about its axis in response to displacementof said other end,
 3. an electrical resistance element coiled externallyaround said former and its rib,
 3. mechanical damping means mounted foractuation by said intermediate member and having a. a variable volumechamber comprising a flexible bellows having rigid end closure walls,one of said walls being provided with a bleed aperture, and b. tworelatively movable components coupled to said end closure walls anddisposed so that said induced relative movement is substantiallyproportional to the relative movement between said two components. 3.mechanical damping means mounted for actuation by said intermediatemember and having a. a variable volume chamber comprising a cylinder anda flexible diaphragm forming one end closure of said cylinder, b. fluidwithin said chamber, and c. two relatively movable components disposedso that said induced relative movement is substantially proportional tothe relative movement between said two components, one of saidcomponents being a member having a part thereof disposed within saidcylinder for action upon said fluid and another part thereof extendingthrough said flexible diaphragm and connected to said intermediatemember.
 3. A vehicle having axles; ground engaging wheels mounted onsaid axles; springs acting on said axles; a load-carrying structuresupported by said springs for relative movement with respect to ground,which relative movement has contributed to it by each axle an effectiveproportion constituting a primary relative movement; and weighingapparatus to be responsive to variations in load carried by the vehicleand to be utilized when the vehicle is in motion, said weighingapparatus comprising: A. an electrical indicator, B. in association withone of said axles, a sensor having two relatively movable elements whoserelative movement is in use induced by a said primary relative movementto produce a correspondingly varying signal; and C. mechanical low-passfiltering means in association with said sensor to attenuate suddenvariations of the primary relative movement which would otherwiseproduce sudden variations of the induced relative movement, saidmechanical low-pass filtering means comprising
 4. Weighing apparatus forincorporation in a vehicle having an axle structure, ground engagingwheels mounted on said axlE structure, springs acting on said axlestructure, and a load-carrying structure supported by said springs forrelative movement with respect to ground whereby while the vehicle is inmotion the two said structures attain an average relative position inaccordance with weight imposed on said load-carrying structure, saidweighing apparatus comprising: a. a spiral spring; b. means for couplinga first of said structures to one end of said spiral spring to causeangular displacement of said one end; c. electrical transducer means forsupplying an electric signal in accordance with said average relativeposition of the two said structures, and comprising
 4. an elongatecontact element, and
 5. means mounting said contact elementlongitudinally of said former for contacting portions of said electricalresistance element above said rib; d. damping means having a viscoussubstance therein; and e. means for coupling said damping means betweensaid other end of the spiral spring and the second of said structures todamp out sudden variations in the position of said other end of thespiral spring relative to the second of said structures.
 5. A vehiclehaving axles; ground engaging wheels mounted on said axles; springsacting on said axles; a load-carrying structure supported by saidsprings for relative movement with respect to ground, which relativemovement has contributed to it by each axle an effective proportionconstituting a primary relative movement; and weighing apparatus to beresponsive to variations in load carried by the vehicle and to beutilized when the vehicle is in motion, said weighing apparatuscomprising: a. an electrical indicator, b. in association with one ofsaid axles, a sensor having two relatively movable elements whoserelative movement is in use induced by a said primary relative movementto produce a correspondingly varying signal; and c. mechanical low-passfiltering means in association with said sensor to attenuate suddenvariations of the primary relative movement which would otherwiseproduce sudden variations of the induced relative movement, said sensorbeing of rheostat type and comprising a generally cylindrical formermounted for angular motion about its longitudinal axis and providedexternally with a rib that follows a helical path of small helix angleabout said longitudinal axis, an electrical resistance element coiledabout said former, and an elongate contact element extendinglongitudinally of said former for wiping engagement of portions of saidelectrical resistance element above said rib.
 6. The combination ofclaim 5, wherein said small helix angle is of the order of 20* of arc.7. A vehicle having an axle structure, ground engaging wheels mounted onsaid structure, springs acting on said axle structure, a load-carryingstructure supported by said springs for relative movement with respectto ground, and weighing apparatus to be responsive to variations in loadcarried by the vehicle and to be utilized when the vehicle is in motion,said weighing apparatus comprising spring means, first means operativeto couple one of two ends of the spring means to a first of saidstructures, electrical transducer means for responding to relativemovement between the other of said two ends of the spring means and thesecond of said structures to supply an electric signal to said indicatorin dependence upon the position of said other end of the spring meansrelative to said second structure, damping means, second means operativeto couple the damping mEans between said other end of the spring meansand the second of said structures to damp out sudden variations in saidrelative position, and electrical indicator means responsive to saidelectric signal to provide a load indication dependent thereon.
 8. Thevehicle of claim 7, wherein said spring means is pre-stressed so as toonly transmit a proportion of the relative movement between said twostructures to said other end of the spring means when the distancebetween said structures is below a predetermined value.
 9. The vehicleof claim 7, wherein the electrical transducer means is of anelectrically inductive character and comprises a linear differentialtransformer.
 10. The vehicle of claim 7, wherein said electricalindicator means comprises a moving-coil type instrument.
 11. The vehicleof claim 7, wherein said first means comprises an abutment membersecured to one of said structures for abutment by the other of saidstructures, and wherein said spring means acts on said abutment member.12. The vehicle of claim 11, comprising restraining means to restrainsaid abutment member from abutment by said structures when the distancebetween said structures exceeds a predetermined value.
 13. The vehicleof claim 7, wherein the electrical transducer means is of rheostat typeand comprises a generally cylindrical former having an electricalresistance element coiled thereon and a contact element disposed forwiping engagement of said electrical resistance element.
 14. The vehicleof claim 13, wherein said generally cylindrical former has alongitudinal axis, is mounted for angular motion about said axis, and isprovided externally with a rib that follows a helical path of smallhelix angle about said axis; and wherein said contact element iselongate, extends longitudinally of said former, and contacts portionsof said electrical resistance element above said rib.
 15. The vehicle ofclaim 14, wherein said small helix angle is of the order of 20* of arc.16. The vehicle of claim 7, wherein said mechanical damping meanscomprises a variable volume chamber.
 17. The vehicle of claim 16,wherein said variable volume chamber comprises a cylinder and a flexiblediaphragm forming one end closure of said cylinder, fluid being providedwithin said cylinder; said damping means further comprising a memberdisposed within said cylinder for action upon said fluid, and anexternal actuator extending through said flexible diaphragm andconnected to said other end of the spring means.
 18. The vehicle ofclaim 16, wherein said variable volume chamber comprises a flexiblebellows having rigid end closure walls, one of said walls being providedwith a bleed aperture.